Thyroid neoplasia, follicular

Membrane and cytoplasmic expression of MIB-1 (Ki-67 equivalent) in some types of follicular thyroid neoplasia, namely in the hyalinizing trabecular... 

Hepatocellular neoplasia in mice Thyroid follicular-cell neoplasia in rats... 

C cells in normal glands have an exclusive intrafollicular topography and are concentrated at the junctions of the upper and middle thirds of the lobes (Fig. 10.19). In patients with multiple endocrine neoplasia, type 2 (MEN2), C-cell hyperplasia has been recognized as the precursor of medullary thyroid carcinoma. Detailed immunohistochemical studies have shown that C-cell hyperplasia is characterized by increased numbers of C cells within the follicles in the same regions of the gland where C cells normally predominate (Fig. 10.20). These relationships are maintained in areas of more advanced C-cell hyperplasia, where C cells often completely encircle and displace the follicular epithelium centrally. Nodular hyperplasia is characterized by the complete obliteration... 

The proposed origin of tumors with mixed medullary and follicular features has been controversial. Volante and coworkers have proposed an origin from two different progenitors. According to their hypothesis, neoplastic transformation of C cells leads to the development of medullary thyroid carcinoma with entrapped normal follicles. Stimulation of the entrapped follicular cells results in hyperplasia and ultimately follicular (or papillary) neoplasia (hostage hypothesis). Neoplastic C cells and follicular cells would have the capacity to metastasize and could explain the presence of both components in distant sites. 

Pathological criteria for classifying thyroid cancer may show discrepancies in the differentiation between foUicu-lar adenoma and minimally invasive follicular carcinoma, and between follicular neoplasia and the folficular variant of papillary carcinoma (Lloyd et al., 2004 Saxen et ai, 1978). The inclusion of papillary microcarcinomas (1.0 cm or less in diameter), which are usually incidental findings or detected by the use of ultrasound-guided thyroid fine-needle aspiration cytology (Lin et al., 1997), the existence of radioactive fallout, which may lead to an increase of differentiated thyroid carcinoma and a rise in population age with time, should also be taken into account when analyzing the epidemiology of thyroid cancer. 

The amplification of thyroglobulin, thyroid peroxidase and TTF-1 mRNA can be a valuable sensitive method for the detection of micrometastases, minimal residual cancer cells and circulating tumor cells of papillary and follicular thyroid carcinoma. TTF-1 can be also used for the detection ofthyroid medullary carcinoma and different lung neoplasia derived from alveolar cells type II and Clara cells (mainly adenocarcinoma). The presence of circulating tumor cells is associated with poor prognosis and... 

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